JPH04133327A - Method of finely processing semiconductor - Google Patents

Abstract

PURPOSE:To execute a very fine processing operation without using a resist by a method wherein a pattern is drawn directly on the surface of a semiconductor by using an electron beam and the pattern is etched. CONSTITUTION:By using an electron beam aligner, a diffraction grating pattern of 235nm intervals on an InP substrate 1 of a compound semiconductor is irradiated with an electron beam. Parts irradiated with the electron beam are denoted by reference numeral 2. Irradiation conditions with the electron beam are as follows: an accelerating voltage of 50keV; a beam current of 60pA; a beam diameter of 15nm; and a dose of 3.36nC/cm. After the electron beam has been irradiated, the surface of the InP substrate 1 is etched by using a mixed liquid of bromine water (Br+H2O) with phosphoric acid.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a semiconductor microfabrication method in which a concavo-convex pattern is formed by etching, which utilizes the difference in etching speed between an electron beam irradiated area and a non-irradiated area. By forming unevenness using the wafer, the processing accuracy of the semiconductor element is improved, the yield is improved, and the manufacturing process is simplified.

[Conventional technology]

In order to form a fine uneven pattern on the surface of a semiconductor, the conventional methods are (1) applying a resist film to the surface of the workpiece, (2) irradiating (exposure) with light, electron beams, or X-rays, and ( 3) Perform development to remove the resist film in the irradiated or non-irradiated areas; (4) Using this remaining resist film as a mask, use an appropriate etching solution to remove the parts of the material that are not covered by the resist film. The steps of (5) removing the resist film after etching was completed were performed in order.

The minimum processing size is 0.5 when exposed to normal light.
The limit is μs. This limit is due to the diffraction effect of light that occurs when a photomask on which a processed pattern is drawn is used for exposure. To perform even finer processing, interference exposure using optical interference fringes (holography) and electronic exposure using electron beam irradiation to draw images are used. The typical processing dimensions of these are 0.1 to 0.2 μm.

Further, as an etching method, in addition to a method using a liquid (wet etching), a method using gas or plasma (dry etching) is also used.

[Problem to be solved by the invention]

However, conventional microfabrication methods involve complicated steps such as resist coating, exposure, development, etching, and resist removal, so they have the disadvantage of poor working efficiency and poor yield.

In addition, since processing accuracy depends on the photosensitive performance of the resist,
There were limits to miniaturization.

An object of the present invention is to solve the above problems and provide a semiconductor microfabrication method that can be processed without using a resist.

[Means for Solving the Problems] The semiconductor microfabrication method of the present invention draws a pattern to be etched on the semiconductor surface with an electron beam, and distinguishes between the areas irradiated with the electron beam and the areas not irradiated. It is characterized by forming unevenness on the semiconductor surface due to the difference in etching speed.

[For production]

When a semiconductor is irradiated with an electron beam, a difference in etching rate occurs between the irradiated area and the non-irradiated area. Therefore, a pattern is drawn directly on the semiconductor surface using an electron beam and then etched. According to this method, there is no need to use a resist, and since direct drawing is performed using an electron beam, very fine processing is possible.

Changes in etching rate due to electron beam irradiation have been confirmed as a phenomenon. The cause of this phenomenon is not clear, but it is thought to be related to crystal defects caused by electron beam irradiation.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention, and shows a structure in which a diffraction grating pattern is formed on a substrate.

In this example, an electron beam exposure device was used to irradiate an InP substrate 1, which is a compound semiconductor, with a sweeping electron beam in a diffraction grating pattern of 235n++M@. The electron beam irradiation section is indicated by reference number 2. The electron beam irradiation conditions are acceleration voltage:
5QkV Beam current: 60pA Beam diameter: 150m Dose amount +3.36 nC/cm.

After electron beam irradiation, the surface of this InP substrate 1 was etched with a mixed solution of bromine water (Br+LD) and phosphoric acid.

A secondary electron micrograph of the surface of the InP substrate 1 after etching is shown in FIG. The length of the white line visible at the bottom center of the photograph is 198 nm. However, in this photograph, a resist was applied before irradiation with an electron beam, the electron beam was irradiated through the resist, and etching was performed after the resist was completely removed.

As is clear from the photograph, since the etching rate of the portion irradiated with the electron beam was faster than that of other portions, a diffraction grating-like uneven pattern was obtained according to the irradiation pattern. Considering that absorption and forward scattering of electrons occur by the resist, it is thought that a more precise pattern can be formed by direct irradiation without a resist.

In the above embodiments, a case was explained in which a pattern was formed in InP, but similar results have been obtained with semiconductors such as InGaAsP, 5InGaAs, and the present invention can be implemented in the same manner. It is also believed that other semiconductors such as Sl, GaAs, and GaP can be used.

As the etching method, not only wet etching but also dry etching can be used to carry out the present invention.

It is also possible to irradiate the electron beam through the resist, so
The same substrate can be partially microfabricated using a resist mask, and other parts can be microfabricated using the method of the present invention.

〔Effect of the invention〕

As explained above, the semiconductor microprocessing method of the present invention directly irradiates the semiconductor surface with an electron beam without using a resist, so it is possible to perform ultrafine processing without affecting the photosensitivity of the resist or forward scattering. There is an effect that makes it possible. Furthermore, since the working process is simplified, working efficiency is improved and the processing yield is also improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the present invention. FIG. 2 is a secondary electron micrograph showing the crystal structure of the example. 1... InP substrate, 2... Electron beam irradiation section. Patent applicant: Optical Measurement Technology Development Co., Ltd. Agent: Patent Attorney Naotaka Ide 兇 Ryo

Claims (1)

[Claims] 1. In a semiconductor microfabrication method in which a semiconductor is etched according to a predetermined pattern, a pattern to be etched is drawn on the semiconductor surface with an electron beam, and a portion irradiated with the electron beam and the irradiated portion are drawn. A semiconductor microfabrication method characterized by forming unevenness on a semiconductor surface due to a difference in etching rate between the etching rate and the unetched portion.